The present invention relates generally to semiconductor wafers and, more particularly, to a method for non-destructive removal of cured epoxy from the backside of a semiconductor wafer.
A semiconductor wafer may undergo a coating process wherein the backside of the wafer is coated with epoxy. The coating may serve as a barrier to light or as a protective coating. It is possible for the coating process to result in an unsatisfactory coating, for example due to particular airflow patterns or curing temperatures in a curing oven, resulting in not fully cured or unevenly cured epoxy. In such a case, it is desirable to remove the epoxy coating without damaging the wafer in order to save and recoat the wafer.
Prior to full or partial curing of the epoxy coating, the epoxy is still soft and can be wiped off, leaving the wafer backside ready for a reapplication of the coating. However, once the epoxy coating is partially or fully cured, it hardens and can no longer be wiped off. Traditional methods of removing cured epoxy from the wafer backside include grinding off the hardened epoxy from the wafer backside. Aside from being messy, removal by grinding generally stresses the wafer and removes some of the wafer backside surface along with the hardened epoxy, reducing the wafer thickness and resulting in a more fragile wafer. Additionally, the hardened epoxy coating may be uneven to begin with, causing the grinding process to damage the wafer backside surface when an attempt is made to grind off the uneven remains of hardened epoxy.
Accordingly, a need exists for a method for non-destructive removal of cured epoxy from the backside of a semiconductor wafer.